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Lower strength steels have traditionally been considered to be immune to embrittlement in the presence of hydrogen gas. In this work, it is demonstrated that contrary to conventional wisdom, there are two regions of fatigue crack growth where hydrogen gas causes significant accelerations in crack propagation rates compared to air. Environmental influences in these two regimes are shown to be dominated by entirely different mechanisms.
We use Type Ia supernovae studied by the High-z Supernova Search Team to constrain the properties of an energy component that may have contributed to accelerating the cosmic expansion. We find that for a flat geometry the equation-of-state parameter for the unknown component, αx = Px/ρx, must be less than -0.55 (95% confidence) for any value of Ωm, and it is further limited to αx < -0.60 (95% confidence) if Ωm is assumed to be greater than 0.1. These values are inconsistent with the unknown component being topological defects such as domain walls, strings, or textures. The supernova (SN) data are consistent with a cosmological constant (αx = -1) or a scalar field that has had, on average, an equation-of-state parameter similar to the cosmological constant value of -1 over the redshift range of z ~ 1 to the present. SN and cosmic microwave background observations give complementary constraints on the densities of matter and the unknown component. If only matter and vacuum energy are considered, then the current combined data sets provide direct evidence for a spatially flat universe with Ωtot = Ωm + ΩΛ = 0.94 +/- 0.26 (1 σ).
Abstract The palladium‐catalyzed defluorinative coupling of 1‐aryl‐2,2‐difluoroalkenes with boronic acids is described. Broad functional‐group tolerance arises from a redox‐neutral process by a palladium(II) active species which is proposed to undergo a β‐fluoride elimination to afford the products. The monofluorostilbene products were formed with excellent diastereoselectivity (≥50:1) in all cases, and it is critical, as traditional chromatographic techniques often fail to separate monofluoroalkene isomers. As a demonstration of this method's unique combination of reactivity and functional‐group tolerance, a Gleevec® analogue, using a monofluorostilbene as an amide isostere, was synthesized.
Molecular characterization of infectious mouse mammary tumor viruses (MMTVs) has been hampered due to the problem of cloning a full-length exogenous virus into a plasmid. The present report describes our strategy for obtaining a full-length clone of an exogenous MMTV from a mouse mammary tumor that arose spontaneously in a wild Chinese mouse free of endogenous MMTV and shows that the cloned virus (JYG-MMTV) is expressed in rat RBA cells. Four-week-old C58/J x CBA/CaJ female mice, free of both endogenous and exogenous MMTVs, were injected with virus-secreting RBA cells. The progeny of these mice were bred, and their offspring were tested for the presence of MMTV. These third-generation mice were found to actively produce MMTV that was shed in their milk and transmitted to their offspring. The virus was detected not only in the mammary glands of these young mice, but also in their spleens and bone marrow. These results suggest that our plasmid-cloned exogenous JYG-MMTV is infectious. This virus can now be used effectively in manipulating the various genes of JYG-MMTV and other MMTV strains to understand their structure/function relationships.
Research Article| June 01, 1999 Chronostratigraphy of the Miocene–Pliocene Sagantole Formation, Middle Awash Valley, Afar rift, Ethiopia Paul R. Renne; Paul R. Renne 1Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 947092Department of Geology and Geophysics, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar Giday WoldeGabriel; Giday WoldeGabriel 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Search for other works by this author on: GSW Google Scholar William K. Hart; William K. Hart 4Department of Geology, Miami University, Oxford, Ohio 45056 Search for other works by this author on: GSW Google Scholar Grant Heiken; Grant Heiken 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Search for other works by this author on: GSW Google Scholar Tim D. White Tim D. White 5Laboratory for Human Evolutionary Studies, Museum of Vertebrate Zoology6Department of Integrative Biology, University of California, Berkeley, California 94720 Search for other works by this author on: GSW Google Scholar Author and Article Information Paul R. Renne 1Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, California 947092Department of Geology and Geophysics, University of California, Berkeley, California 94720 Giday WoldeGabriel 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 William K. Hart 4Department of Geology, Miami University, Oxford, Ohio 45056 Grant Heiken 3Los Alamos National Laboratory, Los Alamos, New Mexico 87545 Tim D. White 5Laboratory for Human Evolutionary Studies, Museum of Vertebrate Zoology6Department of Integrative Biology, University of California, Berkeley, California 94720 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1999) 111 (6): 869–885. https://doi.org/10.1130/0016-7606(1999)111<0869:COTMPS>2.3.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Paul R. Renne, Giday WoldeGabriel, William K. Hart, Grant Heiken, Tim D. White; Chronostratigraphy of the Miocene–Pliocene Sagantole Formation, Middle Awash Valley, Afar rift, Ethiopia. GSA Bulletin 1999;; 111 (6): 869–885. doi: https://doi.org/10.1130/0016-7606(1999)111<0869:COTMPS>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Sagantole Formation comprises more than 200 m of lacustrine, alluvial, and volcaniclastic sediments, plus compositionally bimodal tephras and basaltic lavas, exposed in a domelike horst named the Central Awash Complex in the southwestern Afar rift of Ethiopia. The Sagantole Formation is widely known for abundant vertebrate faunas, including the 4.4 Ma primitive hominid Ardipithecus ramidus. New lithostratigraphic data are used to subdivide the Sagantole Formation into the Kuseralee, Gawto, Haradaso, Aramis, Beidareem, Adgantole, and Belohdelie Members, in ascending order. The members are defined on the basis of lithologic differences and laterally continuous bounding tephras.40Ar/39Ar dating of 12 intercalated volcanic units firmly establishes the age of the Sagantole Formation to be 5.6 to 3.9 Ma, significantly older than previous proposals based on erroneous correlations. Magnetostratigraphic data reveal eight paleomagnetic polarity zones, which can be correlated unambiguously with the Thvera, Sidufjall, Nunivak, and Cochiti Subchrons of the Gilbert Chron. Thus, by reference to the geomagnetic polarity time scale, seven additional chronological datums can be placed in the Sagantole Formation. With a total of 19 such datums, the age resolution anywhere in the Sagantole Formation is better than ±100 k.y., making this the best-dated Miocene–Pliocene succession in Africa. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
A microbial culture enriched from a trichloroethene-contaminated groundwater aquifer reductively dechlorinated trichloroethene (TCE) and tetrachloroethene (PCE) to ethene. Initial PCE dechlorination rate studies indicated a first-order dependence with respect to substrate at low PCE concentrations, and a zero-order dependence at high concentrations. Studies of TCE and vinyl chloride (VC) dechlorination indicated a first-order dependence at all substrate concentrations. VC had little or no effect on the initial rate of TCE dechlorination. With subsaturating concentrations of chlorinated ethenes, nearly stoichiometric amounts of the toxic intermediate vinyl chloride accumulated prior to its dechlorination to ethene. In contrast, under saturating conditions, in which a dense, nonaqueous-phase liquid existed in equilibrium with the aqueous phase, the chlorinated ethene was dechlorinated to ethene, at a rapid rate, with the accumulation of relatively small amounts of chlorinated intermediates.
